Method for protecting hot metal surface

ABSTRACT

Process for preventing the oxidation of hot metallic surfaces comprising coating the surfaces of the hot metal with a reducing agent which forms a protective pellicle, i.e., a thin skin or film, through which the state of the metal surface can still be observed during fabrication. The pellicle or film inhibits the formation of an oxide crust. The metal may be in solid or molten condition. The pellicle is formed by applying a reducing agent to the metal surface. The reducing agent may be applied as a cloud of fine particles, as a solution, or as vapors.

United States Patent 1191' Schaumburg METHOD FOR PROTECTING HOT METALSURFACE [76] Inventor: Georges W. Schaumburg, 1 bis Rue de Londres,Montigny-Les-Metz, France [22] Filed: Jan. 30, 1970 [21] Appl. No.:8,099

' Related U.S. Application Data Continuation-impart of Ser. No. 640,816,May 24,

1967, Abandoned.

[30] Foreign Application Priority Data May 24, 1966 France 6647309 [52]U.S. Cl 72/46, 106/54, 117/16, 117/23, 117/49, 117/129, 117/135.1

[51] Int. Cl B211) 45/02 [58] Field of Search 106/204, 52, 63,

[ Oct. 16, 1973 3,489,578 l/1970 Pugh 106/286 2,529,344 11/1950 Machlet106/286 3,158,515 ll/l964 Michael 148/27 3,537,917 11/1970 Spencer eta1. 148/l2.1 2,762,115 9/1956 Gates 29/424 2,831,782 4/1958 Zvanut29/528 2,842,837 7/1958 Huet et a1. 29/528 2,880,855 4/1959 Nachtman29/528 2,885,315 5/1959 Milliken l48/13.l 2,962,808 12/1960 Cole et a].29/528 2,990,610 7/1961 Luckerath et a1. 29/528 Primary Examiner-WilliamD. Martin Assistant Examiner-Theodore G. Davis Att0rneySughrue,Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT Process for preventing theoxidation of hot metallic surfaces comprising coating the surfaces ofthe hot metal with a reducing agent which forms a protective pellicle,i.e., a thin skin or film, through which the state of the metal surfacecan still be observed during fabrication. The pellicle or film inhibitsthe formation of an oxide crust. The metal may be in solid or moltencondition. The pellicle is formed by applying a reducing agent to themetal surface. The reducing agent may be applied as a cloud of fineparticles, as a solution, or as vapors.

' 5 Claims, No Drawings METHOD FOR PROTECTING HOT METAL SURFACE CROSSREFERENCE TO OTHER APPLICATIONS This application is acontinuation-in-part of U.S. application Ser. No. 640,816, filed May 24,1967 and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention concerns a new process for the protection of solid or liquidhot metallic surfaces.

2. Description of the Prior Art It is known that surfaces of the typewhich are treated in the iron and steel industry have a tendency tooxidize, the more so the higher their temperature.

This oxidation generates internal and surface faults. Moreover, itconstitutes an unfavorable economic element since in the dressing andtransformation of steel it can represent the generation more than 20kilograms of unusable material per tone of metal.

Processes are known which protect iron and steel parts by applying aprotective or reduction layer before submitting them to treatment.However, on the one hand, these known layers are applied cold on thepart which must subsequently be heated, and on the other hand, the knownprocesses form a crust which masks the surface of the part.

An object of the present invention is to protect not only solid but alsoliquid hot metallic surfaces from oxidation. A further object issimultaneously to minimize the formation of oxides.

SUMMARY OF THE INVENTION The process in accordance with the inventioncomprises applying,to the metallic surface to be protected, a productpossessing reduction properties, which gives rise to a protectivepellicle and can, as a result, be introduced and continuously applied,without modification of the manufacturing procedure already existing inthe works of shop floors of the iron and steel industry, in forging orin foundry work.

Contrary to the prior art, the process in accordance with the presentinvention is applicable to a metallurgical part in the course oftransformation or working, for example, in the course of a rollingoperation, without it being necessary to heat the part solely andseparately before the application of the coating. On the other hand, theprotected pellicle, in accordance with the invention, reduces the oxidesand minimizes the formation of calamine and leaves the hot surfacevisible so that one can observe with the naked eye the quality and stateof the surface of the part in the course of lamina- .tion. As soon as afault appears on the surface, it can be seen with the naked eye, sinceit is not masked by a crust of oxides, as in the case of known prior artprocesses.

DETAILED DESCRIPTION OF THE INVENTION The protective composition of thepresent invention has particular applicability to cleaning andprotecting of steel, which is subjected to temperatures of between 900C.and 1,200C during the usual rolling operation on a rolling mill. Steelbars being rolled frequently circulate at a speed of about 50 meter persecond and their cross-sectional surface can be reduced from 3 feet X 3feet to a one-sixth inch diameter wire after 25 passages between thecylinder.

Protective coatings of the prior art applied before passing in therolling mill become rapidly inefficient after a few passages, because ofthe enormous difference of the cross-sections. If these coatings areapplied after the rolling operation, they are no longer useful.Furthermore, the metal would have to be reheated in order to form aprotective pellicle.

0n the contrary, applicant's composition applied to a steel surface isable to permanently protect the metal surface throughout the rollingoperation, no matter how great the cross-section reduction. Furthermore,using the heat produced in the rolling operation, it is not necessary toemploy any exterior heat source in order to form the pellicle.

The materials of this invention may be easily applied to the metalsurface using already existing rolling mill equipment, without any otherconstruction than mounting a transverse tube about 5 feet in length andan aerosol producing apparatus (such as a hopper, turbine, venturi orthe like). No other special preferential circuit or general installationis required. The surface defects of the steel bar may be viewed as soonas they appear during the rolling operation, as the steel surface iskept permanently clean and protected against oxidation.

The chemical forming materials of the present invention may be selectedfrom a wide variety of materials which possesses the necessary chemicaland physical properties required to insure the desired protective andreducing rolls of the present invention. That is, the materials to beemployed in the process of the present invention are those which form apellicle when'heated, suppress oxide formation on the surface of themetal to be protected and which form a film through which the surface ofthe metal can be observed. Such materials can comprise either mineral ororganic components.

As mineral compositions which have been found to be suitable for use inthe process of the present invention, there may be mentioned:

a. SiO A1 0 CaO, MgO, Na, K, and B 0 b. SiO Na CO and B203;

c. SiO K Na CO NaNlL, and HPO d. SiO A1 0 CaO, and MgO;

e. Na B O SiO and CaO.

The above mixtures, as well as those of the following examples, havebeen found to be absolutely non-toxic and very efficient in theprotection of steel at forging temperatures of between 900 and 1,200C.

As organic compositions which have been found to be suitable for use inthe process of the present invention, there may be mentioned mixtures ofcellulose, a vegetable oil, such as palm nut oil, arachis oil, sunfloweroil or the like, together with at least one material selected from amongbentonite clay, chalk or carbon black.

The following illustrative examples will more clearly indicate thenature of the composition of the present invention. The compositionsillustrated in Examples 1-5, inclusive, represent the initialcompositions as applied to the hot metal surface, and not the finalmakeup of the coating.

EXAMPLES 1-3 The following table illustrates three compositions whichare particularly suitable for application to ferrous metals during afoundry rolling operation. In claims 1-5, all proportions are set forthin parts by weight.

TABLE 1 Example C110 S102 A1103 F1220; MgO B K Na EXAMPLES 4 & 5

The following table illustrates two compositions which are particularlysuitable for application to nonferrous metals during foundry rollingoperations.

TABLE 2 Example 0210 810; A1 F 0; MgO T10 Be Na These materials arecontacted with the hot metal surface in the same manner as described forthe compositions of Examples 1-3.

EXAMPLE 6 An organic composition particularly suitable for spraying ontometal billets during foundry rolling operations was prepared by mixingthe following ingredients:

Ingredient Proportion (weight percent) Cellulose 30 Palm nut oil 24Bentonite clay 2] Carbon black 25 In use, the above composition is mixedwith alcohol to obtain a sprayable paste which is then sprayed onto ametal billet during rolling. This composition provides an excellentprotective coating which can be easily removed, if desired, when themetal has cooled.

As indicated in the above examples in accordance with the process whichis the subject of the invention, the reducing, pellicle-formingmaterials are generally solid and may be used in the form of a cloud ofvery fine powder, the particles of which melt upon contact with the hotpart of the liquid metal. As a result there is deposited apellicle whichensures rigorous protection, whilst exercising a chemical energyreduction. The compositions of this invention may also be employed inconjunction with a suitableliquid carrier, for example, as a dispersion,in the form of a fog which also gives rise, on contact with the hotsurface part or the liquid metal, to a protective reducing pellicle. Thereducing agents can also be directly gasified so as to constitute anatmosphere which possesses the property of reducing oxides, and which iscontacted with the hot metal surface in a reducing atmosphere to form aprotective pellicle.

It will be understood that the process which has been described can beused in all industries which put into use oxidizable metals andespecially in the iron and steel industry, in forges or in foundries.

For example, in the case of a lamination, it will be seen that theapplication of a process in accordance with the invention can beeffected without having to modify the lamination train, i.e., themechanical treatment applied to the parts in the course oftransformation, when the parts are at the desired temperature. Theprotective and reducing pellicle in accordance with the invention,maintains the surface of the part substantially free of oxides, leavingany possible superficial fault exposed to the naked eye and this, inspite of the large increase in surface observed in the course oflamination. The operation in accordance with the invention is thuscomparable to sanding, grinding or chemical removal which permitssuppression of masking or observation of surface faults. On thecontrary, it has nothing in common with the known processes of thermaltreatment which consists in applying a coating on the final cold partbefore passing it to an oven or a vat.

The process possesses the following principal advantages:

a. complete or substantial obviation of faults which may result from hotoxidation,

b. elimination of a large part of oxides which increase themanufacturing costs of oxidizable metals,

c. protection of metallic parts which can thus be stocked in theatmosphere without fear of attack. The protection obtained in accordancewith the invention can possibly be used to form a marine coating,

d. since the treatment is effected continuously, it does not limit theproduction capacity in existing installations in which one puts it intopractice. More especially, this treatment does not necessitate anyspecial procedure, and

e. the treatement in accordance with the invention can be effectedautomatically without the intervention of a workman and it can beincorporated conveniently in existing manufacturing procedures withouthaving to modify them. In particular, since the treatment is applied toa part in the course of hot working or transformation and not on thecold part, it does not necessitate subsequent heating of the part, forexample, by passing it through an oven as a separate treatment step.

What is claimed is:

l. A continuous process for forming a protective coating on hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,supresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 17.5 parts CaO, 5.5 parts SiO 1.4 parts A1 0 0.5 part Fe O 1.6parts MgO, 14 parts B, 0.5 part K and 0.3 part Na.

2. A continuous process for forming a protective coating of hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,suppresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 16.0 parts CaO, 4.5 parts SiO 3.6 parts A1 0 0.8 part F6 0,, 2.4parts MgO and 17 parts B.

3. A continuous process for forming a protective coating of hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,suppresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 25.0 parts CaO, 7.0 parts S10 4.2 parts A1 0 1.2 parts Fe,O 3.2parts MgO and 17 parts Na.

4. A continuous process for forming a protective coating of hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,suppresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 17 parts CaO, 5 parts SiO 5 parts Al, 2 parts Fe O 1.8 partsMgO, 37 parts TiO and 2.1 parts Na.

5. A continuous process for forming a protective coating of hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,suppresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 22 parts CaO, 4 parts SiO 4 parts A], 1.5 parts Fe O 1.8 partsMgO, 12 parts TiO 10 parts Be and 1.7 parts Na.

2. A continuous process for forming a protective coating of hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,suppresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 16.0 parts CaO, 4.5 parts SiO2, 3.6 parts Al2O3, 0.8 part Fe2O3,2.4 parts MgO and 17 parts B.
 3. A continuous process for forming aprotective coating of hot ferrous metals during a hot foundry rollingoperation comprising continuously contacting the hot ferrous metal,during hot rolling thereof, with a chemically reducing composition whichforms a pellicle when heated, suppresses oxide formation on the surfaceof the ferrous metal being coated and forms a film through which thesurface can be observed, whereby said protective coating is formed uponcontact of said composition with said ferrous metal, said chemicallyreducing composition having the following initial composition, in partsby weight, 25.0 parts CaO, 7.0 parts SiO2, 4.2 parts Al2O3, 1.2 partsFe2O3, 3.2 parts MgO and 17 parts Na.
 4. A continuous process forforming a protective coating of hot ferrous metals during a hot foundryrolling operation comprising continuously contacting the hot ferrousmetal, during hot rolling thereof, with a chemically reducingcomposition which forms a pellicle when heated, suppresses oxideformation on the surface of the ferrous metal being coated and forms afilm through which the surface can be observed, whereby said protectivecoating Is formed upon contact of said composition with said ferrousmetal, said chemically reducing composition having the following initialcomposition, in parts by weight, 17 parts CaO, 5 parts SiO2, 5 parts Al,2 parts Fe2O3, 1.8 parts MgO, 37 parts TiO2 and 2.1 parts Na.
 5. Acontinuous process for forming a protective coating of hot ferrousmetals during a hot foundry rolling operation comprising continuouslycontacting the hot ferrous metal, during hot rolling thereof, with achemically reducing composition which forms a pellicle when heated,suppresses oxide formation on the surface of the ferrous metal beingcoated and forms a film through which the surface can be observed,whereby said protective coating is formed upon contact of saidcomposition with said ferrous metal, said chemically reducingcomposition having the following initial composition, in parts byweight, 22 parts CaO, 4 parts SiO2, 4 parts Al, 1.5 parts Fe2O3, 1.8parts MgO, 12 parts TiO2, 10 parts Be and 1.7 parts Na.